Method and apparatus for effecting article transfer through the use of magnetic fields

ABSTRACT

Method and apparatus for effecting the transfer of articles from one traveling belt to another belt disposed transversely thereto, without the employment of guide rails, or the like to produce said transfer. The transfer operation is effected by the controlled application of magnetic forces.

[ Aug. 20, 1974 United States Patent [191 Mojden [56] References CitedUNITED STATES PATENTS METHOD AND APPARATUS FOR EFFECTING ARTICLETRANSFER 8 mu MUM 2 O Y me .m M u "m nnm 0U CBM 070 937 0099 HHH 500 0 2640 93 472 23 w m a m m N H G n A e M m. F 0 0 M E S W U a E a H u a T ww U n o m R m Hm v TF .m

Primary Examiner-Richard A. Schacher Assistant Examiner-Douglas D. Watts[73] Assignee: Fleetwood Systems, Inc.,

Countryside, Ill.

Attorney, Agent, or Firm-Olson, Trexler, Wolters, Bushnell & Fosse, Ltd.

[22] Filed:

Feb. 7, 1972 21 Appl. No.: 220,968

[57] ABSTRACT Method and apparatus for effecting the transfer of ar-Related US. Application Data [63] Continuation of Ser. No. 119,506,March I,

abandoned [52] US. 198/20 R, 198/41 [51] Int. B65g 47/00 operation iseffected by the controlled application of a w m m w a P D 9 5 m w m C C8 r. m c H e n g a m 6 R 1 3 n 5 7 l 92 W O 2 2 1 4 0O 9 1 h m a e S f.0 d l. e .1 F l. 00 5 METHOD AND APPARATUS FOR EFFECTING ARTICLETRANSFER THROUGH THE USE OF MAGNETIC FIELDS REFERENCE TO RELATEDAPPLICATION This application is a continuation of application Ser. No.119,506, filed Mar. 1, 1971 and entitled METHOD AND APPARATUS FOREFFECTING ARTICLE TRANSFER, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to magneticconveyor apparatus. More specifically, this invention is concerned witha novel transfer method and arrangement wherein the cans are transferredfrom one traveling belt to another belt, disposed transversely thereof,

using only magnetic forces.

Magnetic conveyors are in wide use today by can manufacturers and othersutilizing can bodies as container mediums. In many instances, the cansused are of the type wherein the product trade dress is applied by alithography process prior to filling and packaging. With lithographedcans, it is desirable to employ a conveyor system that is free of bendsand sharp turns in order to insure against damage to the can surfaces.However, quite often the physical plant layout, as well as the nature ofthe operations to be performed, are such that the conveyor system cannotavoid abrupt changes in direction. Accordingly, it is not uncommon for amanufacturer to find numerous cans wherein the lithography has becomescratched or otherwise marred after processing and transporting over thelength of the conveyor system.

The primary cause or source of damage to the lithography is the mannerin which the various turns and bends in the conveyor system arenegotiated. More specifically, the the general construction of theapparatus in use today is such that curved guide rails are employed inconjunction with transversely oriented traveling belts. With thisarrangement, the cans are forcibly moved through the turns andtransferred from one belt to the other by the back pressure created fromthe downstream flow of can bodies. Accordingly, the cans are subject todamage from two sources; namely, engagement with each other andengagement with the guide rails.

With the present invention, the above-discussed disadvantages of theprior art systems are eliminated. That is to say, the various turns andchanges in direction that must be undergone in a conveyor system arenegotiated without the use of guide rails and without bunching orcollecting of the can bodies at the transfer location and without theresulting employment of back pressure to effect movement of the cans tothe receiving belt. In addition, the spacing between can bodies ismaintained, which is often important and required by the machineryreceiving the cans for the subsequent processing or packaging operation.Basically, these advantages are realized by utilization of a novelarrangement wherein a magnetic field is established at the transferpoint which is effective to forcibly convey the can bodies from onetraveling belt to the other without the employment of any side guides orthe like. It should be noted however, that guide rails may be employedas a safety factor when the transfer is taking place at a locationspaced above personnel, a walkway, or machinery which could be fouled bya can body. But even when guide rails are used, the cans will negotiatethe turns without engaging the guide rails, under normal operatingconditions.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a transferlocation for a conveyor system constructed in accordance with thepresent invention;

FIG. 2 is a top, plan view of the transfer location of FIG. 1,illustrating in phantom, the positioning of magnetic means for therespective conveyor sections;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2, in thedirection indicated;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 2 in thedirection indicated;

FIG. 5 is a partial, sectional view taken along the line 55 of FIG. 2 inthe direction indicated;

FIG. 6 is a partial, sectional view of the incoming conveyor, takenalong the line 66 of FIG. 2, and including a schematic graph of themagnetic field provided in the transfer area;

FIG. 7 is a top, plan view of an alternate form of magnetic arrangementfor the receiving belt.

FIG. 8 is a sectional view of the'magnetic arrangement of FIG. 7, andincluding a graph of the magnetic field created by this arrangement; and

FIG. 9 is a sectional view taken along the line 9-9 of FIG. 8 in thedirection indicated.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring now to the drawings,in FIG. 1 there is illustrated transfer apparatus constructed inaccordance with the present invention, and designated generally 10. Thetransfer apparatus 10 is comprised of a pair of transversely disposedconveyor units 12 and 14. Conveyor unit 12 functions as the incomingsection of the apparatus 10, in that the cans 16 are initially beingtransported by this section. Conveyor unit 14, on the other hand, is thereceiving section of the apparatus 10, the cans 16 moving off of unit 12onto unit 14, as shown, said movement being effected by the novelmagnetic transfer arrangement of the present invention, which will bedescribed in more detail hereinafter.

In the illustrated embodiment of this invention, both conveyor units 12and 14 are of generally similar construction. As such, unit 12 will bedescribed in detail with reference to FIG. 2. In order to avoidunnecessary structural recitation, the same reference characters primedare applied to the corresponding elements of conveyor unit 14.

More specifically, the unit 12 includes a nonmagnetic housing 20 havingguide rollers 22 and 24 at 1 opposite ends thereof. If desired,additional rollers may to one of the guide rollers, roller 22 in thisinstance, in

order to provide the necessary operating power. In addition, there isprovided a stationary magnetic arrangement 34 which is disposed withinhousing 20 in underlying relation to the upper belt'reach 28 so as toestablish a magnetic field of sufficient strength to maintain cans 16 inproper position on belt 26.

in 'FIG. 5. This magnetic arrangement 34 includes a number of sectionsor segments of ceramic, magnetic material 42 which are positioned inend-to-end relation to define an elongate assembly. Mounted in abuttingrelation tothe sides of the ceramic magnetic sections I 42 are a pair ofspaced, elongate pole plates 44 and 46, which are magn etizable metaland positioned to underlie closely the upper surface 30 of housing 20.These pole plates 44 and 46 function as the south and north poles,respectively, of the magnetic arrangement 34 and are narrow in width,with respect to the width of the ceramic magnetic section 42. Thisconstruction provides a focusing effect for the field of flux lines 48which comprise the magnetic field produced by the arrangement 34.Accordingly, as the belt 28 is traveling over the upper surface 30 ofthe housing, the magnetic field 48 will act upon the can bodies 16 tomaintain them in proper position and to resist any tendency of the cansto topple or move transversely of the belt surface.

The magnetic arrangement 34', for the conveyor unit 14, is of adifferent construction from the arrangement 34 of conveyor unit 12.Primarily, the magnetic arrangement 34 is comprised of a first section50 and a second section 52 spaced from the transfer zone 40 asillustrated in FIG. 2. The construction of the firstsection 50 isillustrated in FIGS. 3 and 4, and, as will be discussed hereinafter,this first section 50 extends at least to the edge of the transfer zone40. It is the magnetic field created by the section 50 that produces themovement of the-can ends from belt 28 to the transversely disposed belt28, as illustrated. A construction of the'second section 52 will bealluded to only briefly, and it should be noted that this section may beconstructed in a manner similar to the magnetic arrangement 34, asdescribed previously with reference to FIG.

Directing attention to FIGS. 2 and 6, it can be seen that the poleplates 44 and 46, for the magnetic arrangement 34, terminate atapproximately the edge of zone 40, the ceramic magnetic elements 42being spaced a distance from said zone. The first portion 50 of themagnetic arrangement 34', on the other hand,

extends into this zone 40. This arrangement represents a preferred formof the invention, and one found to work well in practice; however, it isenvisioned that alternate constructions may be employed to attain thedesired operation, such as that shown ln FIGS. 7-9, to be discussedhereinafter. I

Basically, in conveying can bodies, it is desirable to maintain the canbodies under the influence of a magnetic field at all times in order toprevent toppling or transverse movement of the bodies. In order toeffect transfer of the cans 16 from the traveling belt 26 to the belt26", without the use of guide rails and while maintaining the cans underthe influence of a magnetic field, it is necessary that the strength ofthe magnetic field, created by the first section of arrangement 34', bestronger than the magnetic field produced by arrangement 34 in the zone40. It is also desirable to have the strength of the magneticfield 34diminish in the zone 40. In addition, the magnetic field produced byarrangement 34', must be of a control form so as to attain the desiredtransfer action without producing toppling of the can bodies 16. Withthis in mind, attention is now invited first to FIG. 6 and then to FIGS.3 and 4 wherein preferred constructions of the magnetic arrangement 34and first magnetic section 50 for arrangement 34 are illustrated.

As can be seen from FIG. 6, the end of the ceramic magnetic element 42is spaced from the non-metallic conveyor housing 20 and,correspondingly, is spaced a distance from the'transfer zone 40. Therespective pole plates 44 and 46, however, extend beyond the end of themagnet means 42 to approximately the edge of the transfer zone 40, noteFIG. 1. As a result of this construction, the strength of effectivenessof magnetic field 48, represented by the dashed-line graph of FIG. 6,will diminish in a direction towards the zone 40. This particulararrangement is preferred to facilitate the transfer operation. That isto say, the decreasing strength of field 48 enables the field producedby the hereinafter to be discussed magnetic section 50, to effect thetransfer operation smoothly and without mishap.

Considering FIG. 3 next, there is illustrated a transverse, sectionalview of the aforementioned first section 50, and it can be seen that thegeneral arrangement is somewhat similar to that described with referenceto FIG. 5. More specifically, the first section 50, of the magneticarrangement 34, is comprised of two series or stacks of ceramic,magnetic elements 54. The respective stacks 54 are mounted within aU-shaped, non-magnetic housing 55 and rest upon a back plate 56 formedof steel or some other magnetic material. The back plate 56 forms asegment of the magnetic circuit linking the stacks 54. In addition, thestacks 54 are separated by a central spacer 58 which also rests upon theback plate 56 and is constructed of wood or some other non-magneticmaterial. The entire assemblage is held in place by a bolt arrangement60, as illustrated, said arrangement 60 also being constructed of anonmagnetic material or otherwise properly shielded so as not tointerfere with the magnetic circuit existing between the stacks ofceramic, magnetic elements 54. As such, the individual stacks ofmagnetic elements 54 and back plate 56 function and may be viewed as aU- shaped magnet.

In order to focus, and otherwise control the magnetic field thusproduced by the stacked magnetic elements 54, a pair of elongate poleplates 62 and 64 are used, one being mounted atop each stack, asillustrated. Respective pole plates 62 and 64 are disposed between theupper surface of the ceramic, magnetic elements 54 and the surface 30'of the non-magnetic housing 20'. Accordingly, there is produced amagnetic field designated generally 66 which extends between therespective pole plates 62 and 64, and intersects the can bodies 16 beingcarried by the belt 28' to maintain these bodies in position thereon.

Turning now to FIG. 4, and keeping in mind the general construction ofthe magnetic section 50 as discussed above, this figure illustrates alongitudinal, sectional view of said section 50. Accordingly, inconjunction with FIG. 4, the transfer operation and the function of thesection 50 of the magnetic arrangement 34 in this operation will now bediscussed. FIG. 4 is a view taken through the transfer zone 40 which, itwill be recalled, is the location wherein the upper reaches 28 and 28'of the respective traveling belts 26 and 26 overlap. When a can firstenters the zone 40, it will be under the influence of the magnetic field48 created by the magnetic arrangement 34 of conveyor 12. However, ascan 16 progresses into the zone, the effect of field 48 lessens asillustrated in FIG. 6, and the can commences to be influenced by thefield 66 produced by section 50 of the magnetic arrangement 34.Continued advancement increases the force exerted on the can by field 66causing the can body to move transversely toward the edge of the belt28. This movement of the can 16 off belt 28 is realized due to theincreased strength of the field 66, in conjunction with the decrease inthe strength of field 48. Accordingly, once the magnetic field 66overcomes the effect of field 48, the cans will be forcibly moved off ofthe traveling belt 26 and onto the upper reach 28' of the belt 26.

A graph of the strength of the field 66 produced by the magneticarrangement 34' is illustrated in FIG. 4 and designated generally 70. Itshould be noted, that this graph is schematic, and is divided up intofour separate sections labeled A-D" which may also be viewed ascorresponding to the underlying zones or areas of the transferapparatus.

In the area of section A, there exists a flux gradient for the magneticfield 66, in that said field is not at its ultimate strength, which isnot attained until some point within section B of the graph. Thisgradient under section A, is achieved due to the fact that the poleplates 62 and 64 extend beyond the ends of the magnetic section 50, asshown in FIG. 4.

Accordingly, as the cans 16 come under the influence of the magneticfield 66 in zone 40, the transversely disposed orientation of this fieldexerts a pulling force on the can bodies, moving them across the beltreach 28 toward the edge thereof. This effect of the magnetic field 66gradually increases as the can bodies 16 progress into the zone 40,until the effect of the magnetic field 48 is completely overcome. Atthis time, the flux gradient existing in zone A forcibly will move thecan bodies 16 toward the area of higher flux strength, corresponding tothe section B of the graph 70. When an equalized state is reached, thecan 16 will be in zone B with its base resting entirely upon the upperreach 28' of belt 26' or, alternately, the cans will have been moved toa position wherein a significant portion of their bases rest on the belt28. In both instances, the frictional forces created by engagement ofthe can bodies with the traveling upper reach 28' will facilitate, ifnot complete, the transfer operation.

It should be noted, that this transfer operation is attained entirelywith the controlled application of magnetic forces, there being no guiderail, or the like, used which could engage and damage the lithographmaterial on the can body.

Once the can body is properly positioned on the traveling belt reach 28,there is no longer any need for the increased strength of the magneticfield 66 which corresponds to the section B of graph 70. Accordingly, itis contemplated that the strength of this field 66 is to be reduced andthat this reduction is to take place gradually as indicated by section Cof said graph. The final value to which the strength of field 66 is tobe reduced is represented by section D of the graph and is of sufficientstrength to maintain the can bodies in position. In the illustratedembodiment, the magnetic field represented by section D of the graph, isattained by the aforementioned second section 52 of themagnetic-arrangement 34'.

In order to attain the gradual reduction in the strength of the field66, as discussed above, the nonmagnetic housing 55 is provided with atapered end wall 72, and the individual ceramic, magnetic elements 54are positioned as illustrated in FIG. 4. In this regard, a non-magneticspacer 74 is employed in conjunction with the lowermost ceramic elements54. The pole plates 62 and 64 may extend from the stacked ceramic,magnetic elements 54 of the first section 50 to the second section 52,wherein they overlie a ceramic magnet 76 which provides a magnetic fieldof considerably less strength than the stacked arrangement of section50.

In summary, the method of transfer employed by the present invention maybest be characterized as follows:

the can bodies 16 are initially handled by the conveyor unit 12 withproper positioning being maintained by the field 48 of the magneticarrangement 34; next, as the cans 16 enter the transfer zone 40, theinfluence of field 48 is reduced, such that said cans will be subjectedto the magnetic field 66; this field 66 is of a strength greater thanthe field 48 and of a controlled form or shape wherein a flux gradientis created that forcibly moves the can bodies 16 transversely of thebelt 26 and off said belt onto the upper reach 28 of the traveling belt26'; once on belt 26, that portion of field 66, created by section 52 ofmagnetic arrangement 34, maintains the cans in position.

FIGS. 7-9 illustrate an alternate construction for the initiallymagnetic segment of the receiving conveyor. This arrangement may beemployed in place of the previously discussed magnetic portion 50, andis designed to provide a more controlled and defined flux distribution.

The magnetic section of FIGS. 7-9 is designated generally 80, andincludes a number of ceramic magnetic elements 82, upon which aremounted pole plates 84 and 86. The ceramic magnetic elements 82 aredisposed within a nonmagnetic housing 88 which includes a truncated,rearward portion, discussed more fully hereinafter.

Abutting the rearward, truncated portion of the housing 88, is amagnetic section 90 identical in construction to the previouslydiscussed section 52, shown in FIG. 5. That is, section 90 includes aceramic magnetic element 92 having pole plates 94 and 96 engaged againstthe sides thereof.

As was the case with the sections 50 and 52 previously discussed, thestrength of the field produced by section 90 is less than the maximumstrength produced by magnetic section 80. Also, with the construction ofsection there is attained zones of varying flux strength similar tothose previously discussed. As such, a graph of flux strength isincluded in FIG. 8 and identified as 100. This graph, like that employedin FIG. 4, includes four zones; i.e., zone A representing an increasingflux gradient employed in the initial stages of the transfer operation;zone B, the zone of maximum flux strength; zone C, a transition zone;and zone. D,

representative of the strength of the magnetic field employed tomaintain the cans on the conveyor belt after transfer is completed.

As a practical matter, the construction of the magnetic section 80 issuch as to minimize the problems encountered in moving a can body from azone of high magnetic strength, zone B, to a zone of lower magneticstrength, zone C. If this transition is too abrupt, opposing forces arecreated which tend to hinder can movement. That is, the bottom of thecan is being engaged by the traveling belt 26', while the prevailingmagnetic flux tends to prevent movement of the can out of the zone ofmaximum strength.

To attain the aforementioned gradual transition, several innovativechanges are utilized. More specifically, the forward portion of section80 is comprised of two stacks, 102 and 104, of ceramic, magneticelements 82, as shown in FIG. 9. Interposed between said stacks 102 and104 is a non-magnetic spacer 106, while the spacer 106 and said stacksrest on a magnetizable back plate 108. This back plate 108 completes themagnetic circuit between the respective stacks, and in conjunction withspacer 106, produces what may be considered a U-shaped or horseshoemagnet effect.

As can be seen from FIG. .8, the rearwardmost portion of section 80 iscomprised of a reduced number of magnetic-elements 82, a pair of spacedelements 82 being shown in the illustrated embodiment. The rearwardmostelements 82 are also provided with an edge 109 out on a bias, whichconfiguration facilitates the desired gradual reduction in magneticstrength from zone B to zone D. In addition, a magnetized back plate 110is employed with this rearward portion. However, to prevent a shuntingof the respective magnetic circuits, a nonmagnetic spacer element 112 isinterposed between said plate 110 and the stacks 102 and 104. Also, arear spacer element 114 is used for a similar purpose with regard tomagnetic element 92 of section 90. Further, it should be noted that thepole plates 84 and 86 also are cut on a bias, such that they narrow inthe area of engagement with the magnetic element or elements of saidrearward portion. This narrowing of the pole plate 84 and 86 and therearward magnetic element 82, in conjunction with the employment of areduced number of said elements 82 in said rearward portion, permits theattainment of a gradually reducing flux gradient represented by zone C.Accordingly, the

It is to be understood, that the specific arrangement, construction andmethod of operation of the embodiments illustrated in FIGS. l-9,represent but perferred forms of the present invention. As such, thoseskilled in the art, equipped with the present disclosure, may readilydevise alternate arrangements to perform the same function as thepresent invention. For example, in place of the illustrated arrangementwherein the disposition of the north and south poles of the respectivemagnetic arrangements 34 and 34, with regard to the path of travel,remains constant after transfer is completed. It is envisioned that itwill be possible to employ an alternate construction wherein thedisposition of the north and south poles for the arrangement 34' arereversed. In this regard, both arrangements 34 and 34' would extend intothe transfer zone. This alternate embodiment is but one of manyvariations that may be employed, said variations being too numerous toelaborate upon. However, insofar as any alternate embodiments orvariations fall within the spirit and scope of the present invention, asdefined by the claims appended hereto, they are contemplated.

What is claimed is:.

1. Transfer apparatus for a magnetic conveyor system for articles, orthe like, wherein the direction in which articles are traveling is to bealtered, said apparatus including first conveyor means upon which thearticles are initially to be conveyed, and second conveyor means towhich the articles are to be transferred disposed transversely to andintersecting the path of travel of said first conveyor means, said firstand second conveyor means including, respectively, first and secondtraveling endless belts upon which the articles can be supported, theupper reach of said first belt closely overlying the upper reach of saidsecond belt, the area of overlap of said upper belt reaches defining atransfer transition from zone B to zone D can be made smoothly andwithout disruption of can movement.

area, and magnetic means disposed beneath the upper reach of said secondbelt and extending in a direction from said transfer area along the pathof travel of said second belt, said magnetic means producing a magneticflux distribution that is effective to cause articles to move off saidfirst traveling belt and on to said second traveling belt.

2. Transfer apparatus according to claim 1 wherein said first conveyormeans also includes magnetic means for retaining articles in positionthereon.

3. Transfer apparatus according to claim 2 wherein said magnetic meansfor said second belt include a first segment and a second segment, saidfirst segment having a portion thereof extending beneath said transferarea, and producing a stronger magnetic field than said second segmentand the magnetic means for said first conveyor means.

4. Transfer apparatus for a magnetic conveyor system for can bodies orthe like, wherein the direction in which can bodies are traveling is tobe altered, said apparatus including a first conveyor assembly uponwhich the cans are initially being conveyed, and a second conveyorassembly to which the cans are to be transferred, said conveyorassemblies including, respectively, first and second driven endlessbelts upon which the can bodies are supported, the upper reach of saidfirst endless belt closely overlying the upper reach of saidsecondendless belt, and being disposed transversely to said second belt, thearea of overlap of said belts defining a transfer area; and magneticmeans disposed beneath portions of the upper reaches of said belts tomaintain the can bodies in position thereon, with the magnetic means forthe second belt underlying said second belt in the vicinity of saidtransfer area and extending from said transfer area along said secondbelt, with said magnetic means for said second belt producing a magneticfield extending into said transfer area, and having a flux gradientincreasing in the direction of travel of said second belt, at least fora portion thereof, to cause the can bodies to move off said first beltand on to said second belt.

5. Transfer apparatus as defined in claim 4 wherein said magnetic meansfor said second conveyor assembly include a first segment and a secondsegment, said first segment having a portion thereof extending beneathsaid, transfer area, and producing a stronger magnetic field than saidsecond segment and the magnetic means for said first conveyor assembly.

means, with respect to the direction of belt travel, are identical.

8. Transfer apparatus as defined in claim 4, said magnetic meanscomprising one or more ceramic magnetic elements and a pair of elongate,spaced pole plates mounted thereon in underlying relation to therespective traveling belts, one said plate providing a north pole andthe other a south pole.

1. Transfer apparatus for a magnetic conveyor system for articles, or the like, wherein the direction in which articles are traveling is to be altered, said apparatus including first conveyor means upon which the articles are initially to be conveyed, and second conveyor means to which the articles are to be transferred disposed transversely to and intersecting the path of travel of said first conveyor means, said first and second conveyor means including, respectively, first and second traveling endless belts upon which the articles can be supported, the upper reach of said first belt closely overlying the upper reach of said second belt, the area of overlap of said upper belt reaches defining a transfer area, and magnetic means disposed beneath the upper reach of said second belt and extending in a direction from said transfer area along the path of travel of said second belt, said magnetic means producing a magnetic flux distribution that is effective to cause articles to move off said first traveling belt and on to said second traveling belt.
 2. Transfer apparatus according to claim 1 wherein said first conveyor means also includes magnetic means for retaining articles in position thereon.
 3. Transfer apparatus according to claim 2 wherein said magnetic means for said second belt include a first segment and a second segment, said first segment having a portion thereof extending beneath said transfer area, and producing a stronger magnetic field than said second segment and the magnetic means for said first conveyor means.
 4. Transfer apparatus for a magnetic conveyor system for can bodies or the like, wherein the direction in which can bodies are traveling is to be altered, said apparatus including a first conveyor assembly upon which the cans are initially being conveyed, and a second conveyor assembly to which the cans are to be transferred, said conveyor assemblies including, respectively, first and second driven endless belts upon which the can bodies are supported, the upper reach of said first endless belt closely overlying the upper reach of said second endless belt, and being disposed transversely to said second belt, the area of overlap of said belts defining a transfer area; and magnetic means disposed beneath portions of the upper reaches of said belts to maintain the can bodies in position thereon, with the magnetic means for the second belt underlying said second belt in the vicinity of said transfer area and extending from said transfer area along said second belt, with said magnetic means for said second belt producing a magnetic field extending into said transfer area, and having a flux gradient increasing in the direction of travel of said second belt, at least for a portion thereof, to cause the can bodies to move off said first belt and On to said second belt.
 5. Transfer apparatus as defined in claim 4 wherein said magnetic means for said second conveyor assembly include a first segment and a second segment, said first segment having a portion thereof extending beneath said transfer area, and producing a stronger magnetic field than said second segment and the magnetic means for said first conveyor assembly.
 6. Transfer apparatus as defined in claim 4 wherein the magnetic means for the first conveyor assembly is constructed so as to produce a magnetic field of lesser strength than that of said magnetic means for said second conveyor assembly.
 7. Transfer apparatus as defined in claim 4 wherein said magnetic means for the first and second conveyor assemblies are constructed and arranged such that the disposition of the magnetic poles of both magnetic means, with respect to the direction of belt travel, are identical.
 8. Transfer apparatus as defined in claim 4, said magnetic means comprising one or more ceramic magnetic elements and a pair of elongate, spaced pole plates mounted thereon in underlying relation to the respective traveling belts, one said plate providing a north pole and the other a south pole. 